AD5203设计的8串白光LED驱动方案

AD5203是ADI公司的集成了SMBus 和PWM输入的8串白光LED(WLED)驱动器,采用电流模式和升压转换器技术,具有高效率.AD5203集成了0.15 Ω, 2.9 A的开关,工作频率在350kHz和1MHz间选择.输入电压从6V到21V,最大输出电压可调至45V,调光频率在200Hz到10kHz间可调,具有LED开路和短路故障保护.主要用在笔记本电脑,UMPC和监视显示器.本文介绍了AD5203主要特性,方框图以及采用无延迟调光模式的SMBus接口, DPWM调光模式的PWM接口和DC电流调光模式的PWM接口的典型应用电路.

8-String, White LED Driver with SMBus and PWM Input for LCD Backlight ApplicaTIons

The ADD5203 is a white LED driver for backlight applicaTIons based on high efficiency, current-mode, step-up converter technology. It is designed with a 0.15 Ω, 2.9 A internal switch and a pin-adjustable operaTIng frequency between 350 kHz and 1 MHz.

The ADD5203 contains eight regulated current sources for uniform brightness intensity. Each current source can be driven up to 30 mA, and the LED driving current is pin adjustable by an external resistor. The ADD5203 drives up to eight parallel strings of mulTIple series connected LEDs with a ±1.5% current matching between strings.

The ADD5203 provides various dimming modes. Each dimming mode is selectable with an external dimming mode selection pin. The LED dimming control interface can be achieved through PWM input and/or SMBus.

The device provides adjustable output dimming frequency range from 200 Hz to 10 kHz by an external resistor and capacitor. The ADD5203 operates over an input voltage range of 6 V to 21 V, but the device can function with a voltage as low as 5.6 V.

The ADD5203 also has multiple safety protection features to prevent damage during fault conditions. If any LED is open or short, the device automatically disables the faulty current source. The internal soft start prevents inrush current during startup. Thermal shutdown protection prevents thermal damage.

The ADD5203 is available in a low profile, thermally enhanced, 4 mm × 4 mm × 0.75 mm, 28-lead, RoHS-compliant lead frame chip scale package (LFCSP_WQ) and is specified over the industrial temperature range of −25℃ to +85℃.

AD5203主要特性:

White LED driver based on inductive boost converter

Integrated 50 V MOSFET with 2.9 A peak current limit

Input voltage range: 6 V to 21 V

Maximum output adjustable up to 45 V

350 kHz to 1 MHz adjustable operating frequency

Overvoltage protection (OVP) up to typical 47.5 V

Built-in soft start for boost converter

Drives up to eight LED current strings

LED current adjustable up to 30 mA for each channel

Headroom control to maximize efficiency

Adjustable dimming frequency: 200 Hz to 10 kHz

LED open and short fault protection

Selectable dimming control interface methods

PWM input

SMBus serial input

Selectable dimming modes

Fixed delay PWM dimming control with 8-bit resolution

No delay PWM dimming control with 8-bit resolution

Direct PWM dimming control

DC current dimming control with 8-bit resolution

General

Thermal shutdown

Undervoltage lockout

28-lead, 4 mm × 4 mm × 0.75 mm LFCSP_WQ

AD5203应用:

Notebook PCs, UMPCs, and monitor displays


图1.AD5203电路方框图

图2.AD5203典型应用电路:采用无延迟调光模式的SMBus接口

图3.AD5203典型应用电路:采用DPWM调光模式的PWM接口

图4.AD5203典型应用电路:采用DC电流调光模式的PWM接口